1. Field of the Invention
The present invention relates to a vehicle having crawlers or endless tracks and, more particularly, to a vehicle suited for going up stairs and running along paths having various obstacles.
2. Description of the Prior Art
Endless tracks on tanks and bulldozers are known as means for enabling these vehicles to run on rough roads or off-roads. The endless tracks are quite effective when the vehicle runs on soft grounds or slopes, but are quite unsuited to go up and down stairs. Namely, when a vehicle having endless tracks starts to ascend stairs, the lugs on the endless belts engage the front edge of the first step of stairs to produce a force to lift the front wheels because the level of the path along which the vehicle runs is discontinuously raised by the first step of the stairs. In this state, the front wheels and, hence, the lugs on the endless tracks engaging the edge of the first step bear a large part of the weight of the vehicle, so that the endless tracks and the edge of the step tend to be damaged or crushed. In such a case, it is not easy for the vehicle to start running up the stairs. During ascending or descending stairs, the vehicle body is placed on the front edges of the steps and thus is inclined to the horizontal. If the stair has a large gradient, therefore, the vehicle may roll down due to unbalance of the weight. To obviate such an accident, it is an effective measure to make the endless tracks have larger lengths. The increased lengths of the endless tracks, however, will increase the resistance encountered when the vehicle turns to the left or right during running.
Under this circumstance, Japanese Patent Laid-Open Publication No. 138071/1981 proposes a vehicle which can freely run on stairs or off-roads having obstacles.
Vehicles of this kind may be used as a running system for maintenance or inspection of equipments in buildings or factories. In order to conduct and accomplish various maintenance and inspection satisfactorily, this type of vehicle is required to have increased freedom of mobility.